Carburetor



May 1936- L. M. CRABB I v 2,040,922

CARBURETOR Filed March 5, 1934 77 v gwomtoz Patented May 19, 1936 UNITED STATES PATENT OFFICE CARBURETOR poration of Delaware Application March 5, 1934, Serial No. 713,977

5 Claims.

This invention relates to carburetors and has particular reference to adjustment of the spring which acts on the air valve, the. purpose of the adjustment being to change the action of the spring in accordance with changes in temperaare.

In a well known type of carburetor in use today, there is what is known as an air valve between the carburetor high speed jet and the throttle valve. 'Inis air valve is in nearly closed position for slow speeds and idling, but as the throttle is opened the inrush of air will open the valve against the expansive force exerted by the spring. It is Well known that with a rise in temperature the air is less dense and the liquid fuel (gasoline) decreases in viscosity so that the carbureted mixture becomes richer with increases in temperature. To compensate for this variation in carbureted mixture due to increase in temperature, there is applied to the spring which governs the air valve a seat composed of a thermostatic metal which flattens with increase in temperature. The flattening of the thermostatic metal valve seat will lessen the expansive force of the spring acting on the air valve and allow the air valve to be opened to a greater degree so that a greater amount of air will be passed and thereby increase the proportion of air to fuel. This increase in the amount of air will give better idling and prevent motor stalling at low and idling speeds, also it decreases fuel consumption and improves warming up and operating condition when cold, through all ranges of speed.

On the drawing:

Figure 1 is a transverse sectional view through a carburetor showing the invention applied and showing in dotted outline another position of the valve and thermostatic seat.

Figure 2 is a sectional view on the line 22 of Figure 1.

Figure 3 is a sectional view of a modification.

Referring to the drawing, the numeral 2 indicates a carburetor as a whole. The intake pipe from the gasoline tank is attached at 4 and de livers the fuel shown at 6 to the float bowl 8 having the usual float l8 therein controlling the usual valve (not shown) in the admission line.

From the float bowl there is an exit passage in the member I2 which delivers into the passage l4 to the low speed jet 16, the tip 18 of which is surrounded by the usual venturi 20. A second member 22 having a passage 24 delivers liquid fuel to the channel 26 which in turn delivers fuel to the high speed jets 28 and 30.

The usual choke valve (not shown) is positioned in the air inlet 32 which takes air from the atmosphere and delivers it to the tips 34 and 36 of the high speed jets and tip 18 of the low speed jet I6.

Above the jets I6, 28 and 38 the carburetor has a riser 38 which connects to the usual riser 40 connected to the usual intake manifold (not shown). In the riser 48 there is located the conventional throttle valve 42.

Pivoted at 44 substantially centrally of the carburetor adjacent the tips 34 and 36 of the jets 28 and 30 is the air valve 46. The air valve has an ear 48 on its back to which there is pivoted at 50 a link or rod 52 having a ball shaped end 54. The ball shaped end 54 seats in the conical end of a piston 56 and an end plate 68 and a ring member 60 hold the ball in the piston end.

'The piston 56 slidably operates in a cylinder 62,

screw threaded as shown at 64 into a boss 65 20 formed on the riser 38.

The end of the cylinder 62 is closed as shown at 64 and a. thermostatic metal spring seat 66 is secured by rivet 68 at the closed end 64. A coil spring 69 is confined in the cylinder between the spring seat 66 and a recess 10 in the piston end. Suitable means (not shown) is provided in the piston 56 so that the same pressure will be maintained on both sides of the piston.

Except for the thermostatic spring 66, the parts so far described are conventional, and form no part .of the invention except insofar as they relate to the combination.

By referring to Figure 1, the full line position shows the position during cold Weather when the liquid fuel 6 has a greater viscosity and the air is denser. For cold weather the thermostatic seat 66 causes more pressure on the spring which closes air valve tighter thus keeping the mixture more nearly correct and not allowing it to lean out due to the viscosity of the gasoline being greater. This is also the case when idling, as the air valve does not close tight but continues to breathe. The spring 69 in the full line position of the parts shown in Figure 1, is fully expanded and exerts a sufficient compressive force on the piston so that the valve 46 will force air to pass through the venturi 28 for idling and slow speeds. When the throttle valve 42 is opened the inrush of air will open the air valve 46 and compress the spring 69 so that the greater the throttle valve is opened the greater will be the inrush of air and the more will the spring 69 be compressed. In cold weather when the air is denser and the liquid more viscous, a proper proportion of mixture can be obtained through the 10 spring 69 from pressing on the air valve 46 and turi 20.

so that the composition of carbureted mixture 7 .remains substantially constant.

With an increase in temperature, the thermostatic spring seat 66'will flatten toward the dotted line position, and'for the higher temperatures it will be in the dotted line position. This will release the as the force of the spring has been decreased, the

incoming air at idling and slow speeds will pushthe air valve 46 slightly open, or to the dotted lineposition. This will allow a greater mixture of air in proportion to liquid'fuel-for the reason that the air is now able to pass from the air entrance 32 to the riser 40 through the opening at the end ofthe air valve 46 and through the venspeed sufficiently high to drawan appreciable amount of fuel from the tips 34an'd 36; For

idling and low speeds, therefore, when the air is less dense and the viscosity of the-liquid higher, there, will be maintained a proportion of -airand gasoline which is comparable to 'the proportions maintained during cold temperatures when the air valve 46 is closedifor idling and slow speeds. V

Instead of the structure of Figure-1, that shown in Figure 3 may be used. In Figure 3 the cylinder: '62 has its end 64 closed The thermostatic spring 66' "is composed of J-shaped bimetallic halves tfiaand 66b secured together by a rivet 61( The spring 66' rests freely on the end 64' and against 7 a disc 'H which abuts against the spring 69.-The operation of the structureof Figure 3 is; the same as that of Figure 1. n I claim:

-1; In a carburetor having a fuel jet andan air valve immediately beyond the jet, a link pivotally connected to the air valve, spring means- At low speeds and at idling the passage of 'air at the airvalve 46 Will not beat a exerting pressure against'the other end of the 7 link, a casing surrounding the spring means and temperature responsive means'engaging the outer end of the spring and the casing to vary the force of the spring in accordance with the temperature.

2. In a carburetor having a, fuel jet and a throttle valve, an air valvebetween the jet and the throttle, means pivotally connected to the air valve to operate the same,'a tubular casing enclosing a spring and. slidable piston, said first named means being connected to the piston, and'temperature responsive means engaging the outer end of the spring and the casing to vary the force exerted by the spring on the piston in accordance with the temperature. a V

3. In a carburetorhaving a fuel jet and an Q air valve immediately beyond the jet, a linkage, directly connected to the valve, coiled spring means bearing'against the linkage to urge the valve to closed position, and temperature responsive means engaging the other end of the spring to vary the force exerted by the spring in accordance with the temperature. ,4. In a carburetor having aniair passage, a valve in said passage, a link pivoted to said valva a tubular casing secured in the passage wallga piston slidably within the casing and connected to the link, a spring bearing against the piston to close thevalve, and temperature responsive means between the opposite end of the spring and the casing to'vary the force exerted by the spring in accordance with the'teniperature.

5. In a carburetor having a fuel jet and'aj throttle valve, an air valvebetween the -jet and the throttle, means constantly urging said 'valve' toward closed position including a rigid nonyieldable memberdirectlyconnected to the valve and a spring acting on said member, and a ther mostatic seat for the said spring to vary the force exerted by the spring in accordance with the temperature. l e,

. g LESTER M. CRABB, 

